Pen-type injector having holding mechanism for medicament cartridge

ABSTRACT

An injection device for injection of a medicament from a medicament cartridge  40  having a neck portion is disclosed. The injection device further comprises a main housing  4  in which the medicament cartridge  40  is releasably retained by first and second retaining means  92,94 . The retaining means  92,94  are each moveable between a first position in which the neck portion is engaged thereby to retain the medicament cartridge  40  in the main housing  4  and a second position which allows the medicament cartridge  40  to be removed from the main housing  4.

The present invention relates to improvements in an injection device,and in particular to improvements in a portable injection device fordispensing controlled quantities of a medicament.

Typically such injection devices are used by those suffering fromdiabetes to administer a dose of insulin or insulin-type medicine tothemselves. It will be understood that such injection devices aresuitable for the injection of other medicines.

At one time, such doses were administered by use of a disposablesyringe; the syringe first being filled from a separate phial or othercontainer and then used to inject the dose. However, there were a numberof difficulties in such an arrangement. In particular, such anarrangement was not suitable for the infirm. For others, the socialstigma associated with such syringes made their public use problematic.

To overcome these difficulties a number of so-called pen-type injectorshave been developed. These devices are small, being capable of beingcarried in a jacket pocket or the like and allow a number of doses to beobtained from a cartridge or ampoule contained within the injector. Thepresent invention has particular application to such pen-type injectors.

While such pen-type injectors are a considerable improvement upondisposable hypodermic syringes, problems nevertheless remain.

The present invention provides for improved ease of use and improvedinteraction with a user.

The invention will now be described, by way of example only, withreference to the accompanying drawings; in which:

FIG. 1 shows a plan view of a pen-type injector in accordance with thepresent invention;

FIG. 2 shows a similar view to FIG. 1 with an end cap of the injectoromitted;

FIG. 3 shows a cross-sectional view of the injector of FIGS. 1 and 2;

FIG. 4 shows an end view of a further injector in accordance with thepresent invention with a cover in an open position to allow extractionof a cartridge;

FIG. 5 shows a similar view to FIG. 4 with the cover closed;

FIG. 6 shows a perspective view of the cover of FIGS. 4 and 5 in an openposition;

FIG. 7 shows details of the cover illustrated in FIG. 6;

FIG. 8 shows the opening mechanism shown in FIG. 7 in an open position;and

FIG. 9 shows a view similar to FIG. 6 with the cover closed.

Referring first to FIGS. 1 to 3, there can be seen a pen-type injector 2in accordance with the present invention. The injector 2 comprises amain housing 4 to which is releasably secured an end cap or cover 6.

At the first end of the main housing 4 there is provided a control panelregion 8. This region includes a display panel 10, typically a LCDdisplay, and a first dose button 12 and a second dose button 14, thefirst and second dose buttons being operated to increase or decrease adose of medicament to be delivered. The control panel region 10 in theillustrated embodiment also includes an arm button 16.

At the first end of the main housing there is also provided a dispensebutton 18. Preferably, when not depressed, the dispense button 18 isflush with the main housing 4.

Along a longitudinal axis of the injector 2, to each side of the controlpanel region 10 are provided a number of grooves or recesses 20. Theseaid in the gripping of the injector 2 by a user.

At a second end of the main housing 4 a needle unit 22 is releasablysecured to the main housing. The second end of the main housing 4 isalso provided with a shaped portion 24.

In use a cartridge 40 or ampoule of medicament is stored in the housing4 behind the shaped portion 24. For preference, the shaped portion istransparent to permit the cartridge 40 to be seen by a user.

A primer button 26 is also provided on the second end of the housing 4.It will be understood that when the end cap 6 is in place over thesecond end of the housing, it will not be possible inadvertently todepress the primer button 26 or to be pricked by the needle unit 22. Acover detection switch 28 may also be included at the second end of themain housing 4 to detect whether the end cap or cover 6 is in place ornot.

In FIG. 3, there can be seen a priming contact 30, an arm contact 32, afirst dose contact 34 and a second dose contact 36 corresponding to therespective buttons. A dispense contact 19 corresponding to the dispensebutton 18 is also shown.

With reference to FIG. 3 it may be seen that there is provided asuitable location for a power source 38 such as a battery or batteries.There is also a suitable region in which a cartridge 40 or ampoule ofmedicament is to be located. This region may be accessed by way of theremovable shaped portion 24 of the main housing 4 to allow forreplacement of the cartridge 40 or ampoule as required by the user. Analternative cartridge access means is disclosed in relation to FIGS. 4to 9.

In a third region of the main housing 4 there is provided a drivemechanism 42 which operates from the power source 38 and acts upon thecartridge 40 or ampoule of medicament.

The cartridge 40 or ampoule comprises a container 44 or sleeve closed atone end by a cover 46 at a head end thereof, and sealed at the other bya movable bung 48 or stopper. When in position, the needle unit 22pierces the cover 46 and movement of the bung 48 towards the cover 46will cause the medicament contained within the cartridge 40 or ampouleto be expelled. The cartridge may be a 3 ml cartridge in accordance withISO/FDIS 11608 Part 3, or any other suitable cartridge to suit theinjector.

Movement of the bung 48 or stopper is caused by movement of a piston orplunger 50 forming a part of the drive mechanism 42. The piston orplunger 50 is movable between a first fully withdrawn position (notshown) which allows for the replacement of the cartridge 40 or ampouleand a second fully extended portion in which as much medicament aspossible has been expelled from the cartridge 40 or ampoule. An end stopswitch 52 may be provided in the main housing 4 to detect when thepiston 50 is in the fully withdrawn position. Tripping of the switch endstop 52 may release a catch or other fastening device to allow access tothe main housing 4 for replacement of the cartridge 40.

The drive mechanism 42 is operated by a motor 54 under the control of anelectronic control unit (not shown). The motor 54 should be reversiblein order to allow the piston 50 to be moved between the first and secondpositions. In FIG. 3, the motor 54 can be seen to drive the piston 50 byway of a gear train 42, such that rotation of a third rotor 58 causesthe piston 50 to be moved in relation to the third rotor 58.

Preferably, the user can feel the vibration of the motor 54 and theassociated drive mechanism 42 and/or hear them in operation. In this wayan added degree of confidence in the fact of the operation of theinjector 2 is provided to the user.

The control buttons have a number of functions. The dose buttons 12,14allow a user to select a desired dosage. The dose arm button 16 allows auser to confirm selection of a desired dosage. The first dose button canincrement the dosage level and the second dose button can decrement thedosage level. The dose dialling buttons 12,14 may be pressed down (andheld for a short time, 1–2 seconds) to re-set a dose value to zero. Theuser can then dial up (or down) in single (or half) increments.

The dose dialling buttons 12,14 are intended to be pressed once for asingle (or half) increment in the selected dose value. In an alternativeembodiment, pressing and holding one of the buttons will cause the dosevalue to start to scroll (up or down) in order to change the dose sizemore rapidly.

The dispense button 18 allows a user to initiate dispensing of thedosage. The primer button 26 dispenses a unit of dosage from thecartridge 40. Thus, if any air is trapped in the injector 2 this can beexpelled by use of the primer button 26. A door release catch isprovided to allow access to the cartridge 40.

Since the cartridge 40 is of a standard size, each cartridge 40 will beemptied by an identical travel of the plunger driven by the drivemechanism. Once the plunger 50 is in the fully extended position, thecartridge 40 is known to be empty and an indication of this will beprovided to the user.

When the door release catch is operated for the emptied cartridge 40 tobe removed the drive mechanism 42 is operated to reverse a lead screw 60to withdraw the plunger 50 until the lead screw 60 strikes the end stopswitch 52 which is provided at a known reference point.

When a new cartridge 40 is detected, for example by way of a contactswitch (not shown), and the door release catch closed, the electroniccontrol unit advances the lead screw 60 until the plunger 50 strikes thecartridge bung 48. This may conveniently be done by fitting amicro-switch 51, such as a dome contact switch to a free end of theplunger 50.

Since the exact position of the bung 48 can be calculated with referenceto the rear end stop 52, a number of units of medicament stored withinthe cartridge 40 can be determined. Thus a half empty or incorrectlyfilled cartridge 40 may be used with the injector 2 of the presentinvention. The electronic control unit having determined the number ofunits stored within the cartridge preferably will not allow a dosagelarger than that remaining to be dialled up for dispense.

In the embodiment of FIGS. 4 to 9, there can be seen a tab 90. The tab90 is constrained for sliding movement within or on the main housing 4.As seen in FIG. 6, the tab 90 is adapted to slide in grooves 91 providedon the main housing 4. When the tab 90 is withdrawn a slider mechanism(FIGS. 5 to 9) causes first and second jaws 92, 94 to move radiallyoutwardly from a neck of the cartridge 40 or adaptor 43 to allow removalof the cartridge 40.

The slider mechanism can be seen most clearly in FIGS. 6 and 7. Thefirst and second jaws 92, 94 are each disposed on respective elongatearms 93, 95. The arms are adapted to pivot about at point 96 located atends remote from the jaws 92,94. Spring means 97 is provided between thearms 93, 95 to bias the arms away from one another. The slider mechanismis located within a recess formed in the main housing 4. The recess isconveniently provided with walls 98 which act as end stops to limit thetravel of the arms 93,95. Thus once the tab 90 begins to move it isaided by the arms 93,95 separating under the action of the spring means97 until the arms abut the walls 98.

Sliding the tab 90 home conversely pushes the arms 93,95 togetheragainst the action of the spring means 98 and causes the jaws 92, 94 tolock about the cartridge 40 or the adaptor 43 as required. Latchingmeans are provided to retain the tab 90 in the closed position.

1. An injection device for injection of a medicament from a medicamentcartridge having a neck portion, the injection device comprising: a mainhousing in which the medicament cartridge is releasably retained byfirst and second retaining means, the retaining means each beingmoveable between a first position in which the neck portion is engagedthereby to retain the medicament cartridge in the main housing and asecond position which allows the medicament cartridge to be removed fromthe main housing; spring means disposed between the first and secondretaining means to urge the first and second retaining means toward thesecond position; and a slider tab acting on each of the first and secondretaining means to urge the first and second retaining means towards thefirst position.
 2. An injection device according to claim 1, wherein,the slider tab acts on an external face of each of the first and secondretaining means.
 3. An injection device according to claim 1, wherein,the slider tab is slidably retained within a groove formed in the mainhousing.
 4. An injection device according to claim 1, wherein, theslider tab is adapted to engage the neck portion of the medicamentcartridge.
 5. An injection device according to claim 1, wherein, themain housing includes an end stop to prevent movement of the first andsecond retaining means beyond the second position.
 6. An injectiondevice according to claim 1, wherein, the first and second retainingmeans move radially about a common pivot point.